(1) Field of the Invention
The present invention generally relates to patient monitors.
(2) Description of Related Art
Patient monitors are used to monitor numerous physiologic parameters. Some of these parameters, like non-invasive blood pressure, cardiac output, cardiac index, etc., are typically measured at predetermined time intervals and are displayed on the patient monitor until a new reading is taken. In the interim between readings, however, the displayed physiologic readings may no longer be consistent with the monitored patient's actual condition. Further, the initial reading itself may be unreliable because of problems associated with the measurement of the physiologic parameter. Errors could be introduced, for example, by a misplaced sensor or external noise or artifact pickup. Moreover, the reliability of the displayed values of some measured parameters depends on such factors as whether the measurement algorithms has converged, or has a high enough level of statistical confidence, etc.
Given the need to provide expedient care and the obvious serious consequences of basing medical treatment related decisions on stale or otherwise less reliable patient data, there is a need on the part of clinicians to quickly comprehend how reliable, e.g., current, or valid, or accurate, the displayed physiologic readings are.
Some patient monitors on the market, for example, Datascope Patient Monitoring's Spectrum and Passport 2, indicate the elapsed time since a physiologic parameter was measured using a counter adjacent to the reading, i.e., separate from and not unitary with the reading. Others, such as certain Aspect Medical monitors, communicate the quality of a patient signal using a bar graph adjacent to the reading (also separate from and not unitary with the reading). Further, the monitor disclosed in U.S. Pat. No. 6,675,031 displays assessments of quality, such as “INVALID MEASUREMENT” or “WEAK SIGNAL,” next to the displayed patient parameter. These display elements, such as counters, bar graphs, and textual assessments however, do not always stand out, and are easily overlooked in a busy hospital setting. Further, given the large amount of information displayed on a typical patient monitor, the counter or bar graph may not always be read in the context of the physiologic parameter it is actually associated with. They also require the viewer to see, mentally associate, and interpret two different on-screen display elements, usually in a rushed, cluttered and distracting environment.
Certain patient monitors replace displayed patient parameters with dashed lines to the extent the reading exceeds a predetermined threshold error level. One or more Aspect Medical monitors replace the patient parameter numeral with an outline of the numeral or remove the numeral altogether when such a threshold is exceeded, indicating the numerical data may be unreliable.